In cases where filtration devices are used for a long period of time, filtration sands (filtration materials) within filtration tanks (filtration containers) of the filtration devices are clogged by muddiness in unfiltered liquids, such as water, it becomes impossible to perform efficient filtration, and quality of the liquid having been filtered becomes bad. Therefore, when necessary, the mud substance (muddiness) clinging to the filtration materials is removed, and the clogging of the filtration materials is thereby eliminated. For the aforesaid purposes, it is necessary to perform operations for replacing the filtration materials, or operations for manually taking out the filtration materials from the filtration tank, cleaning the filtration materials for peeling off of the muddiness from the filtration materials, and thereafter again returning the cleaned filtration materials into the filtration tanks. In order for the operations described above to be performed, considerable labor is required, and a space for cleaning the taken-out filtration materials becomes necessary. Also, in cases where the filtration materials are to be scrapped, large quantities of industrial scraps arise. Therefore, there have heretofore been known filtration devices for enabling the aforesaid cleaning operations so be performed automatically without a large space being required.
As an example of a filtration device capable of cleaning a filtration material automatically, there has been known a filtration system, wherein a cleaning mechanism (cleaning device) for a filtration material is located within a filtration tank and is actuated at predetermined time intervals, wherein the filtration material is thereby cleaned, and wherein the muddiness having been peeled off the filtration material is discharged from the filtration tank to the outside (patent literature 1, patent literature 2).
In the filtration system described in the patent literature 1, the cleaning device for cleaning the filtration material by rotation of a screw conveyor is located on a support plate for supporting layers of filtration sand. Also, the filtration system described in the patent literature 2 has a constitution, in which the cleaning device for cleaning the filtration material by the rotation of a screw conveyor is hung from an upper section of the filtration tank into the inside of she filtration tank.
Further, there has been known a filtration sand cleaning system, in which a cleaning device is located at the outside of a filtration tank, in lieu of being located at the inside of the filtration tank (patent literature 3). In the cases of the filtration sand cleaning system, there are disclosed a filtration container provided with a filtration material, a pump for sucking out the filtration material from the filtration container, and the filtration material cleaning device for cleaning the filtration material having been sucked out from the filtration container. In the cases of the cleaning system, the pump is connected to the filtration tank and the filtration material cleaning device respectively by pipes. The filtration system is constituted such that the filtration sand containing the muddiness is transferred into the cleaning device, water it supplied by the pump into the cleaning device, and the filtration material from which the muddiness has been removed is returned into the filtration tank. Also, the muddiness having been removed is sucked up by a pump from the upper section of the cleaning device and discharged to the outside through piping connected to the cleaning device.
Patent literature 1:
PCT International Publication No. WO 01/83076
(FIG. 6)
Patent literature 2:
Japanese Unexamined Patent Publication No. 2004-160432
(FIG. 1)
Patent literature 3:
U.S. Pat. No. 5,112,504
(FIG. 1)